Acute inflammatory cell infiltrate, may extend into the mediastinum, with organisation a sequelae - constrictive pericarditis.

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Haemorrhagic pericarditis

Blood plus serous/fibrinous/suppurative and is most commonly seen in malignant neoplastic involvement - may see malignant cellson cytology of a pericardial tap.

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Caseous pericarditis

TB usually.

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Adhesive mediastinopericarditis

Pericardial sac is obliterated with adherence of the external aspect of the parietal layer to surrounding structures ie heart pulling on parietal pericardium and surrounding structures (diaphragm, ribs etc). Increased work load for the heart.

Normally only 30-50mL of clear straw coloured fluid in the pericardial sac. Effusions can contain blood or inflammatory cells. Large pericardial effusions cause a globular enlargement of the heart on CXR. Large effusions that restrict cardiac filing are a medial emergency known as cardiac tamponade.